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Abstract:

Provided is a process for producing aldehydes or ketones by oxidizing
alcohols with oxygen, which comprises oxidizing alcohols to aldehydes or
ketones in an organic solvent at room temperature with oxygen or air as
an oxidant, wherein ferric nitrate (Fe(NO3)3.9H2O),
2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) and an inorganic chloride
are used as catalysts, the reaction time is 1-24 hours, and the molar
ratio of said alcohols, 2,2,6,6-tetramethylpiperidine N-oxyl and the
inorganic chloride is 100:1˜10:1˜10:1˜10. The present
process has the advantages of high yield, mild reaction conditions,
simple operation, convenient separation and purification, recoverable
solvents, substrates used therefor being various and no pollution, and
therefore it is adaptable to industrialization.

Claims:

1. A process for producing aldehydes or ketones by aerobic oxidation of
alcohol comprising a step of oxidizing alcohol to aldehyde or ketone at
room temperature in an organic solvent for about 1 to 24 hours using
oxygen or air as oxidant, and ferric nitrate,
2.2.6.6-tetramethylpiperidinyloxy and inorganic chlorides as catalysts,
wherein a molar ratio of said alcohol to said
2.2.6.6-tetramethylpiperidinyloxy, to said ferric nitrate, and to said
inorganic chlorides is 100:1.about.10:1.about.10:1.about.10.

Description:

[0001] The present invention relates to a process for producing aldehydes
or ketones by aerobic oxidation of alcohols with a ferrous catalyst.

BACKGROUND OF THE TECHNOLOGY

[0002] Aldehydes and ketones are known as important raw materials in fine
chemical industry, and are widely applied in industrial chemical
production as well as in academic research laboratories. Oxidation is a
type of basic and crucial chemical transformation. In industry, aldehydes
and ketones are prepared mainly by oxidation. Hence it is promising to
develop an economic, mild, eco-friendly and efficient catalytic oxidation
method. Traditionally, aldehydes and ketones are prepared by oxidation of
corresponding alcohols using at least stoichiometric amount of oxidants.
Although this protocol enables the preparation of aldehydes and ketones,
however, the use of oxidant such as chromium oxide, manganese oxide and
ruthenium oxide etc., would yield almost the same amount of
oxidant-derived waste, which causes a serious burden to the environment.
Therefore such method is not suitable for large-scale industrial
production (Chromium Oxidations in Organic Chemistry; Springer: Berlin,
1984; Regen, S. L.; Koteel, C. J. Am. Chem. Soc. 1977, 99, 3837-3838;
Griffith, W. P. Chem. Soc. Rev. 1992, 21, 179-185). Thus much attention
has been paid to methods for preparing aldehydes and ketones by catalytic
oxidation of corresponding primary or secondary alcohols using oxygen as
oxidant with transition metals such as Pd, Ru, Mo--Co, Co, Pt, Os--Cu,
Os, Ni, Cu, Fe etc. (Blackburn, T. F.; Schwartz, J. J. Chem. Soc. Chem.
Commun. 1977, 157-158; Piera, J.; Backvall, J.-E. Angew. Chem. Int. Ed.
2008, 47, 3506; Sheldon, R. A.; Arends, I. W. C. E.; Brink, G.-J. T.;
Dijksman, A. Acc. Chem. Res. 2002, 35, 774; Mallat, T.; Baiker, A. Chem.
Rev. 2004, 104, 3037). TEMPO, as a stable oxygen free radical, plays an
important role in synergetic catalytic oxidation with Fe or Cu of primary
or secondary alcohols to prepare the corresponding aldehydes or ketones.

[0003] The present invention overcomes a series of defects of existing
technologies such as the use of heavy metals as catalyst, rigorous
reaction conditions, time-consuming, limited scope of substrates, high
reaction temperature and reaction pressure etc., and thereby provides an
efficient method for preparing aldehydes or ketones by aerobic oxidation
under atmospheric pressure. In said method, ferric nitrate, TEMPO, and
inorganic chlorides are used as co-catalyst, oxygen is used as oxidant,
and thereby brings advantages including the reducing chemical wastes,
pollutions, cost, and various resources for starting materials, as well
as mild reaction conditions and high efficiency. The method according to
the present invention is suitable for large-scale industrial production
and is eco-friendly.

SUMMARY OF INVENTION

[0004] The present invention provides a method for preparing aldehydes and
ketones by a catalytic aerobic oxidation of alcohols under mild reaction
conditions and meanwhile possesses such advantages as high efficiency,
low cost and being eco-friendly.

[0005] The method for preparing aldehydes or ketones by aerobic oxidation
of alcohols according to the present invention comprises a step of
oxidizing alcohol to aldehyde or ketone at room temperature in an organic
solvent for about 1 to about 24 hours using oxygen or air as oxidant, and
using ferric nitrate, 2.2.6.6-tetramethylpiperidinyloxy(TEMPO) and
inorganic chlorides as catalysts, wherein a molar ratio of said alcohol
to said 2.2.6.6-tetramethylpiperidinyloxy, to said ferric nitrate, and to
said inorganic chlorides is about 100:1˜10:1˜10:1˜10.

[0010] The molar ratio of said alcohol to said
2.2.6.6-tetramethylpiperidinyloxy, to said ferric nitrate, and to said
inorganic chlorides according to the present invention is preferably
about 100:5:10:10.

[0011] The present invention discloses a method f or preparing aldehydes
or ketones by oxidation of alcohols in an organic solvent at room
temperature using oxygen as oxidant and Fe(NO3)3.9H2O,
TEMPO (2,2,6,6-tetramethylpiperidinyloxy) and inorganic chloride (NaCl)
as catalysts. The method of the present invention selectively oxidizes an
alcohol with functional groups such as carbon-carbon single bond,
carbon-carbon double bond or a carbon-carbon triple bond etc. with oxygen
in the air or pure oxygen under atmospheric pressure and produces
corresponding aldehyde and ketone of a primary alcohol or a secondary
alcohol by oxidation. The advantages of the method according to the
present invention include high yield, mild reaction conditions, simple
operation, convenient separation and purification of products, recyclable
solvents, various resources for starting materials, being eco-friendly,
and no pollution etc. The present invention is suitable for application
in industrial production.

[0012] One advantage of the present invention is that the substrates are
available from various resources. The present invention uses
Fe(NO3)3.9H2O, TEMPO and inorganic chloride as
co-catalyst, which can catalytic oxidize not only normal alcohols,
benzylic alcohols, enols, cyclic alcohols etc., but also alcohols bearing
much complicated structure such as propargylic alcohol and allenol etc.
The method according to the present invention has advantages of mild
reaction conditions, simple operations, convenient separation and
purification of products, and the solvents being recoverable. Besides,
the method according to the present invention has high yield and catalyst
efficiency. For instance, an effective reaction can be initiated even if
the content of catalysts is as low as 1 mol %. The method of the present
invention overcomes a series of defects of existing technologies such as
use of heavy metals as catalyst, rigorous reaction conditions, the
reaction as being time-consuming, and limited catalyst substrates. The
method of the present invention is not only suitable for small-scale
synthesis in laboratories, but also for large scale industrial
production.

[0013] The method according to the present invention uses oxygen or air,
which is low-cost, and abundant in amount, replacing the chemical
oxidants in conventional oxidation systems. The reaction can be conducted
at room temperature under atmospheric pressure and neutral conditions,
and the operations are convenient and controllable. For example, the
reaction goes on well at room temperature under atmospheric pressure.
Because of the use of oxygen as oxidant in the process according to the
present invention, byproduct of the reaction is water, which will not
result in any pollution to the environment, if treated properly, thus it
is a green chemosynthesis. The present invention with simple working and
high yield, effectively lowers the cost of production.

EMBODIMENTS OF THE INVENTION

[0014] Detailed description will be described now for better understating
of the present invention, but not for limiting the contents of the
present invention.

[0071] Fe(NO3)3.9H2O (16.1607 g, 40.0 mmol), TEMPO (6.2510
g, 40.0 mmol), NaCl (2.3377 g, 40.0 mmol) and DCE(400 mL) were added to a
2 L-three-necked flask, and were stirred for 10 mins at room temperature
under oxygen atmosphere. 1-Phenyl ethanol (488.64 g, 4.0 mol) was then
added dropwise to the reaction solution. The reaction was exothermic, and
the reaction temperature was kept below 50° C. The reaction was
monitored by TLC till it was complete. The reaction solvent DCE was
recovered after distillation under atmospheric pressure (350 mL, recovery
of 88%) and acetophenone was obtained after further distillation under
reduced pressure (b.p. 98˜100° C./20 mmHg, 436.6414 g, 91%).

Examples 29-34

##STR00029##

[0073] Fe(NO3)3.9H2O (0.05 mmol), 1,2-dichloroethane (DCE,
4 mL), TEMPO(0.05 mmol) and additive (0.05 mmol) were added to a 10
mL-three-necked flask and were stirred for 5 mins at room temperature
under oxygen atmosphere. 3-Hexylocta-1,2-dien-4-ol (0.5 mmol) was
dissolved in DCE (1 mL) and then was added dropwise to the reaction
solution. The reaction was monitored by TLC till it was complete. The
resulting reaction solution was diluted with ether (30 mL), dried over
anhydrous MgSO4, filtered by a short pad of silica gel and
condentrated under reduced pressure, and then trimethylbenzene (46 uL)
was added, and conversion and yield were analyzed by nuclear magnetic
resonance spectra (1H NMR, 300 MHz).